Contact lens and method for prevention of myopia progression

ABSTRACT

A method of slowing the progression of myopia in a person, comprises applying to the eye of the person contact lens or lenses each including a vision correction area for correcting in use the myopic vision of a wearer, and a myopic defocus area having a less negative focal power, to simultaneously present a controlled myopic defocus to the retina both when viewing in the distance and also when viewing at near. Contact lenses and their use are also claimed.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/631,124,filed Apr. 24, 2007, the entire content of which is hereby incorporatedby reference in this application.

FIELD OF INVENTION

The invention relates to a contact lens and method for prevention ofmyopia progression.

BACKGROUND

Myopia (also called sort-sight) is a common ocular condition in whichdistant objects appear blurred whereas near objects are seen clearly.The prevalence of myopia, which is about 25% in developed countries andmay be 70-80% in parts of Asia, has significant socioeconomic and publichealth consequences. Even people with relatively low degrees of myopiausually require an optical correction (eg spectacles or contact lenses)to allow them to drive a car or see the school blackboard, whereas thosewith high myopia also have an increased risk of developing blindingconditions such as retinal detachment and glaucoma. Myopia oftendevelops during childhood and typically increases in severity (requiringprogressively stronger spectacles to correct it) until early adulthood,although the final amount of myopia that develops will vary betweenindividuals.

Myopia is generally characterised by an abnormal enlargement of theeye-ball which has the effect of moving the light-sensitive tissue (theretina in the back of the eye) out of the focal plane of the opticalcomponents of the eye. Thus, images of distant objects are brought tofocus in front of the retina, rather than in the plane of the retina.Images of distant objects are therefore seen as blurred. In high levelsof myopia, the marked enlargement of the eye-ball also results in astretching of the retina and its associated blood supply, which rendersthe eye more susceptible to retinal detachment, glaucomatous damage anddegenerative myopic retinopathy.

The aetiology of myopia is poorly understood. Both genetic andenvironmental factors have been implicated and in susceptibleindividuals myopia progression is thought to be associated withexcessive near work (eg reading), possibly because the prolongedmuscular effort of focussing the eyes at near (accommodation) results ina lag of accommodation (insufficient accommodation) and hyperopicretinal defocus. The correction of myopia requires minus-powered lenseswhich demand a greater accommodative effort for near work than isrequired without the lenses. This greater effort (and thus greateraccommodative lag) has been implicated in exacerbating myopiaprogression and attempts have been made to reduce it by prescribingbifocal spectacles or Progressive Addition Lenses (PALs). Most evidenceindicates that if bifocals/PALs slow myopia progression compared toconventional lenses, then it is only by a small amount. A variety ofother methods have been used in attempts to slow myopia progression (egvision therapy, distance under-correction and biofeedback training) butthere is no convincing evidence that myopia progression is reduced bythese procedures. In one recent study (Chung, Mohidin & O'Leary,Undercorrection of myopia enhances rather than inhibits myopiaprogression, Vision Research, 42 (2002) 2555-2559) 47 children had theirmyopia undercorrected by 0.75 D (which reduced their distance vision to6/12). Over a period of two years, the progression of myopia in thesechildren was shown to be significantly greater than in a control groupof children wearing a full conventional correction. They concluded thatmyopic defocus speeds up myopia development in already myopic children.However, although bilateral under-correction results in myopic retinaldefocus for distance viewing, clear retinal images in both eyes areexperienced for near viewing. Use of pharmacological agents, inparticular atropine eye-drops, to reduce myopia progression has beeninvestigated in several studies and recent trials have provided evidencethat repeated instillation of atropine may be effective in reducingmyopia progression. However, myopia typically progresses over a numberof years. The prospect of applying drug therapies long-term to largenumbers of healthy children poses significant problems in relation todrug toxicity and other unwanted side effects.

Animal studies have demonstrated that the normal developing eye grows ina co-ordinated manner so that the length of the eye matches the power ofits optical components, resulting in emmetropia (no refractive error).Furthermore, when a lens is placed in front of a developing animal'seye, the eye alters its growth in such a way as to compensate for theimposed defocus. Over time, the eye adjusts its axial dimensions toachieve functional emmetropia with the lens in place. Thus, eyes thathave worn minus lenses (initially causing hyperopic retinal defocus,with images focused behind the retina) become elongated and are thusmyopic on lens removal. Eyes that have worn plus lenses (causing myopicretinal defocus, with images focussed in front of the retina) areshortened and are thus hyperopic (long sighted) on lens removal. Suchcompensatory responses to defocusing lenses have been demonstrated inseveral species, ranging from chick to monkey.

SUMMARY OF INVENTION

In broad terms in one aspect the invention comprises a contact lensincluding a vision correction area for correcting in use the myopicvision of a wearer, and a myopic defocus area for simultaneously in usepresenting a myopic defocused image to the wearer at all levels ofaccommodation.

In broad terms in another aspect of the invention comprises a method oftreating or slowing the progression of myopia in a person, whichincludes applying to the eye(s) of the person or prescribing for theperson, a contact lens or lens(es) each including a vision correctionarea for correcting in use the myopic vision of a wearer, and a myopicdefocus area which simultaneously in use presents a myopic defocusedimage to the wearer.

The contact lens and method of the invention are aimed at slowing myopiaprogression in humans, in particular in children and young adults. Thelens is intended to correct pre-existing myopia (allowing the wearer tosee distant objects clearly, as a normal contact lens), while alsoincluding a myopic defocus area or ‘treatment zone’ which applies acontrolled myopic defocus to the retina both when the wearer is viewingin the distance and also when viewing at near, in order to slow theprogression of myopia. A focussed retinal image and a myopic defocusedretinal image during both distance and near viewing are simultaneouslypresented to the eye(s) of the wearer.

This invention provides a new means and method for treating myopiaprogression in people with myopia with contact lenses which both correcttheir myopic refractive error and simultaneously provide an opticaltreatment to slow the progression of myopia. The optical treatmentconsists of continuous myopic retinal defocus which is created by thecontact lenses both during distance viewing and also during nearviewing.

The invention also includes use, in the manufacture of a contact lenssystem or kit for treating or slowing the progression of myopia in apatient, of two or more contact lenses which may be the same ordifferent, at least one of which includes a vision correction area forcorrecting in use the myopic vision of the patient and a myopic defocusarea for simultaneously presenting in use a myopic defocused image tothe patient.

The invention also includes a method of correcting myopic vision whilecausing lens-induced functional emmetropia in a person, which includesapplying to at least one of the person's eyes a contact lens including avision correction area for correcting in use the myopic vision of theperson and a myopic defocus area for simultaneously presenting in use amyopic defocused image to the person.

The invention also includes use of a contact lens including a visioncorrection area for correcting in use the myopic vision of a person anda myopic defocus area for simultaneously presenting in use a myopicdefocused image to the person, for the technical purpose of correctingthe person's myopic vision causing lens-induced functional emmetropia onapplication of the contact lens to the person's eye.

BRIEF DESCRIPTION OF THE FIGURES

The invention is further described with reference to the accompanyingFigures, by way of example and without intending to be limiting, inwhich:

FIG. 1 schematically illustrates one form of a contact lens of theinvention, from one side;

FIG. 2 is a front view of another form of a contact lens of theinvention;

FIG. 3 is a front view of a further form of contact lens of theinvention;

FIG. 4 is a front view of yet a further form of contact lens of theinvention;

FIGS. 5 a and 5 b illustrate treatment of myopia progression by themethod of the invention, as referred to further subsequently;

FIGS. 6 a and 6 b are data for 13 myopic children. FIG. 6 a shows theprogressive difference that develops with time between the myopia innormally corrected eyes (SER[dist]) and myopia in eyes experiencingsustained myopic retinal defocus (SER[near]). For these children, eyesexperiencing myopic defocus developed myopia at a rate 0.36 D/year lessthan the normally corrected eyes. FIG. 6 b shows that the vitreouschamber depth (VCD) of the eyes experiencing myopic defocus grew at aslower rate (difference=0.13 mm/yr) than the normally corrected eyes.These data are referred to further in the study results describedsubsequently;

FIGS. 7 a and 7 b show that the changes in myopia progression resultingfrom sustained myopic defocus are well explained by the changes in eyegrowth brought about by the myopic defocus. The slopes of theserelationships (−2.16 D/mm to −2.98 D/mm) are close to the theoreticalvalue (−2.7 D/mm). These data are referred to further in the studyresults described subsequently.

FIG. 8 shows that myopic defocus can readily be induced in either thedominant or the non-dominant eye when accommodating to read at near.These data and their relevance are referred to further in the studyresults described subsequently.

DETAILED DESCRIPTION OF PREFERRED FORMS

Referring to FIGS. 1-4, the contact lenses of the invention comprise acorrection area or zone indicated at 1 a in each of FIGS. 1-4 which hasa focal length which will correct existing myopic vision of a wearer(the correction area or zone 1 a has a negative focal power). The lensescomprise another area 1 b which will simultaneously present a myopicdefocused image to the wearer during both distance and near viewing,which is referred to herein as a treatment zone for convenience. Thatis, the treatment area is relatively less negative in focal power thanthe correction area 1 a. It is possible that the treatment area may beup to 5 dioptres less negative in focal power than the correction area,more likely between 1 and 3 Dioptres less negative and typically about 2Dioptres different. If the correction area for a particular subject withonly mild myopia has a low negative focal power such as only 1 Dioptresnegative for example, then it is possible that the treatment zone mayhave a neutral or low positive focal power.

As shown in FIG. 2, the treatment zone may be composed of two separatepart-circular shaped areas 1 b as shown which impinge onto the area ofthe surface of the contact lens from either side (or above and below)while the balance of the lens comprises the correcting area or zone 1 a.In FIGS. 2-4 the lens is shown in relation to the pupil margin of atypical wearer which is indicated at 2.

In FIG. 3 the treatment zone 1 b which applies myopic defocus comprisesone half of the lens while the correction zone 1 a comprises the otherhalf of the lens. In FIG. 4 the correction zone comprises a centralovaloid area of the lens while the treatment zone 1 b comprises thebalance of the surface area of the lens.

The invention is not limited to particular shapes of the areas of thecorrection and treatment zones on the lens or lenses and the treatmentand correction zones may each make up any part of the area of the lens,provided that the net result is that the lens will simultaneouslypresent to the wearer a clear retinal image and myopic defocus duringboth distance and near viewing. The lenses shown and the shapes of thecorrection and treatment areas are given by way of example only.

FIGS. 5 a and 5 b diagrammatically illustrate the effects of wearing oflenses of the invention and the method of the invention. During distancevision shown in FIG. 5 a, accommodation is relaxed and images of distantobjects are brought to focus on the retina via the correction zone ofthe lens, giving clear distance vision. In each case the correction zoneof the each lens is indicated in solid and the treatment zone as abroken line. Simultaneously, light from the distant objects passesthrough the treatment zone of the lens and is brought to focus in frontof the retina, causing myopic defocus on the retina. Although FIG. 5shows (diagrammatically) the clear retinal image and the myopic defocusapplied to different retinal locations, in reality the two images lieover the same retinal areas.

During near vision, shown in FIG. 5 b, the convergence of the eyesnecessary to maintain single binocular vision (and also the proximity ofthe reading target) cause the eyes to accommodate. In each eye, thisaccommodation brings the image transmitted through the correction zoneinto focus on the retina. This accommodation has the effect ofmaintaining a simultaneous myopic-defocused retinal image created bylight passing through the treatment zone of the lenses.

The Effect on the Eye Over Time

The study described in detail below shows that when sustained myopicdefocus is present in human eyes their rate of myopia progression issignificantly slowed. In this study the dominant eyes of eighteen 11year-old children with myopia between −1.00 and −3.00 D sphericalequivalent were corrected for distance; the fellow eyes wereun-corrected or corrected to keep the refractive imbalance≦2.00 D.Unexpectedly children accommodated to read with the distance-correctedeye, with the result that their under-corrected eye experienced myopicretinal defocus when viewing at both distance and near. Myopiaprogression was followed in both eyes with cycloplegic autorefractionand A-scan ultrasonography measures of vitreous chamber depth (VCD) madeapproximately every 8 months for between 8 and 30 months. Mixed effectsmodelling of the inter-eye differences in refraction and VCD showed thatmyopia progression in the under-corrected eyes was significantly slowerthan in the distance-corrected eyes (inter-eye difference inprogression=0.37 D/yr (95% CI=0.57 to 0.18 D/yr, P=0.0005, n=13);difference in vitreous chamber elongation rate=0.13 mm/yr (95% CI=0.19to 0.08 mm/yr, P=0.0001, n=13)). No inter-eye differences developed forlens thickness (P=0.383), anterior chamber depth (P=0.513) or cornealradius (P=0.537). The study shows that sustained myopic retinal defocusslows the progression of axial myopia in children:

Methods

Participants were 18 children (11 female, 7 male, mean age 11.6 years)with a variety of ethnic origins (10 East Asian, the remainder includedCaucasian, South Asian (Indian) and Maori/Pasifica). Inclusion criteriawere (i) ten to thirteen years of age (ii) no previous spectacle orcontact lens wear (iii) both eyes having subjectively determinedbest-sphere refractions between −1.00 D to −3.00 D withastigmatism≦−1.00 DC and initial anisometropia≦1.00 D (iv) both eyescorrectable to 6/6 Snellen acuity and (v) no binocular visionabnormality or ocular pathology. Stereopsis was assessed using the Wirtcircles of the Stereotest (Stereo Optical Inc, Chicago, USA). Eyedominance was determined using a simple sighting test.

The dominant eyes of all children were corrected for distance becausethis is the most common procedure in monovision contact lens practice.The non-dominant eyes viewed through a plano lens unless the resultantrefractive imbalance between the eyes exceeded 2.00 D, when thenon-dominant eye was partially corrected to keep the imbalance equal to2.00 D. As myopia progressed, the dominant eye was corrected to maintain6/6 acuity while keeping the refractive imbalance no greater than 2.00D. Participants were advised to build up to full-time wear as quickly aspossible. Spectacle wear was either full-time (8 or more hours/day) orpart-time.

Spherical equivalent refraction (SER), measured by cycloplegicautorefraction and vitreous chamber depth (VCD), measured by A-scanultrasonography, were used to monitor myopia progression. Cycloplegiawas induced with 1% Tropicamide (2 drops/eye, 5 minutes apart) aftercorneal anaesthesia with benoxinate: measures were made 30 minuteslater. This protocol produces effective cycloplegia in children of thisage. A portable autorefractor (Retinomax K-plus, Nikon Inc., Tokyo,Japan) was used to obtain 2 measures for each eye. Each measure wasexpressed in power-vector form, with M representing the sphericalcomponent and J₀ and J₄₅ the powers of the equivalent Jackson crosscylinders at axes 0° and 45°. The average M component was used as themeasure of SER. Ocular component dimensions (anterior chamber depth,ACD, lens thickness LT, and axial length, AXL) were measured by A-scanultrasonography (Ophthasonic a-scan/b-scan III, Teknar Inc, St Louis,USA). Vitreous chamber depth was computed as VCD=AXL−(ACD+LT) averagedform three measures for each eye. Measures were made on the dayspectacles were dispensed (baseline) and at follow-up visitsapproximately 8 months apart for an average period of 18.7 months (range8 to 30 months).

The accommodative status of the eyes when reading with the monovisionprescription was determined by Cross-Nott dynamic streak retinoscopy. Inthis method, the working distance is varied in order to find the neutralretinoscopy reflex in each eye. At neutral, the plane of the retinoscopesight-hole coincides with the point in space conjugate with the retina.

Linear mixed-effects models were used to investigate the development ofinter-eye differences over time. The model took account of the pairedeyes, the repeated measures taken on the same eye and importantly, thedifferent number of measurements made per subject. The models were fitin SAS (SAS Institute Inc. USA) using the procedure PROC MIXED and theRestricted Maximum Likelihood (REML) fitting algorithm.

Results

Monovision Spectacle Wear

After several months of adaptation to monovision, dynamic retinoscopy(see Methods) showed that all children (excluding 5 who dropped out ofthe study early) accommodated to read with the distance-corrected(dominant) eye rather than with the near-corrected eye. Consequently,the near-corrected eyes experienced myopic defocus at all levels ofaccommodation. Stereoacuity, which was 40 sec arc prior to recruitment,was typically reduced to between 40 and 80 sec arc with monovision, butreturned to 40 sec arc with a conventional correction. Best-correctedacuity remained at baseline levels (typically 6/5) in all eyes.

Refractive Error Versus Time

The baseline SERs of distance-corrected eyes (−1.61±0.62 D (mean±SD) andnear-corrected eyes (−1.69±0.67 D) were not different (P=0.383). Myopiaprogression during monovision wear, computed as(SER[afterMV]-SER[baseline])×12/(months of wear), gave a meanprogression rate across participants of −0.72±0.32 D/yr indistance-corrected eyes and −0.32±0.30 D/yr in near-corrected eyes. FIG.6A shows how the inter-eye difference in refraction(SER[dist]-SER[near]) developed over time for each of the participantsand also the mixed-model estimate of the average population trajectorywith 95% confidence intervals. The model estimated the averagedifference in myopia progression between the eyes as 0.36 D/yr (95%CI=0.54 to 0.19 D/yr, P=0.0015, n=13) with near-corrected eyesprogressing more slowly than distance-corrected eyes. Similar analysesshowed that no inter-eye differences developed for either J₀ (P=0.14) orJ₄₅ (P=0.15). Analysis of the effect of part-time versus full-time wearof monovision suggested that the difference in progression rate (D/yr)between the two eyes was less in part-time wearers (P=0.04), but thedifference in VCD elongation rate between the two eyes was not differentfor part-time and full-time wear (P=0.11).

Changes in Ocular Dimensions with Time

The mean baseline VCDs of the distance and near-corrected eyes wereequal (17.02±0.63 mm) with ranges of 15.98 to 18.42 mm and 16.04 to18.35 mm respectively. FIG. 6B shows the development of inter-eyedifference in VCD between the distance- and near-corrected eyes(VCD[dist]-VCD[near]) over time for each of the participants. Themixed-model analysis showed the mean difference in vitreous chamberelongation rate equalled 0.13 mm/yr (95% CI=0.18 to 0.08 mm/yr,P=0.0003, n=13), with the near-corrected eyes elongating more slowlythan the distance-corrected eyes. Similar analyses showed that axiallength increased more slowly in near-corrected eyes than indistance-corrected eyes (mean difference=0.10 mm/yr (95% CI=0.19 to 0.02mm/yr, P=0.016, n=13) but no inter-eye differences developed for lensthickness (P=0.253), anterior chamber depth (P=0.509) or corneal radius(P=0.451).

Correlation Between Changes in Refractive Error and Vitreous ChamberDepth

FIG. 7A shows the linear regression relationships between the change inSER during monovision wear (SER[afterMV]-SER[baseline]) and the changein VCD (VCD[afterMV]-VCD[baseline]) for all eyes. With refractive erroras the dependent variable, the slopes of the relationships were similar(−2.16 D/mm, R=0.81, for distance-corrected eyes and −2.22 D/mm, R=0.88,for near-corrected eyes). Thus, although the progression rates weredifferent in the two eyes, both rates correlated closely with increasesin VCD. FIG. 7B illustrates the relationship between the difference inrefractive error (SER[dist]-SER[near]) and the difference in VCD betweenthe distance and near-corrected eyes (VCD[dist]-VCD[near]) at each visitfor each participant. The slope of the relationship obtained by linearregression (not shown) equalled −2.98 D/mm (R=0.72).

The Effect of Eye Dominance

FIG. 8 shows that myopic defocus can readily be induced in either thedominant or the non-dominant eye when accommodating to read at near witha monovision correction. FIG. 8 shows the focal distance in dioptres (ofthe point in space conjugate with the retina) for each eye (ND:non-dominant, Dom: dominant) when reading at three different targetdistances (circles=target at 18 meters; squares=target at 50 cm;triangles=target at 25 cm) while wearing a CL monovision correction.Data are for 10 young subjects (mean age 23 yr), determined using a ShinNippon autorefractor. [A & B] Non-dominant eye distance-corrected, with+4 add (A) or +2.00 D add (B) in Dominant eye. [C] Both eyesdistance-corrected. [D & E] Dominant eye distance corrected, with +2 add(D) or +4.00 D add (E) in Non-dominant eye. Thus regardless ofdominance, accommodation is exerted to bring the distance-corrected eyeto focus on the reading target plane (0, −2 or −4 D) while inducingmyopic defocus in the contra-lateral eye. These results imply thataccommodation while reading is not driven primarily by defocus in eitherthe dominant or non-dominant eye. Rather, accommodation is driven by theconvergence of the eyes necessary to maintain single binocular vision(convergence accommodation) or by proximity cues (proximalaccommodation), or both.

CONCLUSION

Unexpectedly, children wearing a monovision correction accommodated toread with the distance-corrected eye, causing the contra-lateral eye toexperience sustained myopic defocus at both distance and near. Myopiaprogression and the associated abnormal axial growth of the eye weresignificantly reduced in all eyes experiencing sustained myopic defocus.Myopic defocus was induced in the contralateral eye whether the dominantor the non-dominant eye was corrected for distance. This indicates thataccommodation is not driven by defocus in either the dominant ornon-dominant eye, but rather by convergence of the eyes to maintainsingle binocular vision or by proximity cues. The results (surprisingly)indicate that sustained myopic retinal defocus acts as ananti-myopiagenic stimulus that counters abnormal axial elongation of thehuman eye. This conclusion is the opposite of that reached afterbilateral under-correction of children with myopia by Chung et al(Vision Research, 42 (2002) 2555-2559).

The method and contact lenses of the invention in addition to correctingrefractive error, apply continuous myopic retinal defocus in both eyeswhether the wearer is viewing in the distance or at near. The effect ofwearing the new contact lenses is that the myopic retinal defocuscreated by the lenses inhibits the abnormal axial elongation of the eyesthat underlies myopia progression with the effect that over time, theprogression of myopia slows, stops or reverses. The manifestations ofthe effect are (i) the progressive abnormal enlargement of the eyeceases, although depending on the age of the wearer, normal eyeenlargement (growth) may still occur. (ii) the progressively increasingmyopic refractive error, requiring progressively stronger minus powerlenses to correct it, slows its rate of progression or ceases toprogress.

The foregoing describes the invention including preferred forms thereof.Alternations and modifications as will be obvious to those skilled inthe art are intended to be incorporated therein as defined in theaccompanying claims.

1. A method of slowing the progression of myopia of a person,comprising: applying to the eye or eyes of the person or prescribing forthe person, a contact lens or contact lenses, each contact lensincluding a vision correction area to correct the myopic vision of theperson by providing a focussed retinal image; and a myopic defocus areato provide a myopic defocused image to the person during both distanceand near viewing, wherein the focussed retinal image and the myopicdefocused image lie over the same retinal areas, and wherein the contactlens or contact lenses are effective in slowing the progression ofmyopia of the person.
 2. A method according to claim 1, wherein themyopic defocus area has a focal power that is up to 5 dioptres lessnegative than the focal power of the vision correction area.
 3. A methodaccording to claim 1, wherein the myopic defocus area has a focal powerthat is between about 1 and about 3 dioptres less negative than thefocal power of the vision correction area.
 4. A method according toclaim 1, wherein the myopic defocus area has a focal power that is about2 dioptres less negative than the focal power of the vision correctionarea.
 5. A method according to claim 1, comprising applying to the eyeor eyes of the person or prescribing for the person, a contact lens orlenses in which the myopic defocus area comprises two separatepart-circular shaped areas which impinge onto the area of the surface ofthe contact lens from either side or from above and below and in whichthe balance of the lens comprises the vision correction area.
 6. Amethod according to claim 1, comprising applying to the eye or eyes ofthe person or prescribing for the person, a contact lens or lenses inwhich the myopic defocus area comprises one half of the lens and thevision correction area comprises the other half of the lens.
 7. A methodaccording to claim 1, comprising applying to the eye or eyes of theperson or prescribing for the person, a contact lens or lenses in whichthe vision correction area comprises a central ovaloid area of the lensand the myopic defocus area comprises the balance of the lens.
 8. Amethod according to claim 1, wherein the person is a child or a youngadult.
 9. A method according to claim 1, wherein the person is about 23years old or less.
 10. A method according to claim 1, wherein the myopicdefocus area comprises a plurality of areas presenting a myopicdefocused image to the patient during both distance and near viewing.11. A method according to claim 1, wherein the myopic defocus area has afocal power that is between about 1 and about 3 dioptres less negativethan the focal power of the vision correction area.
 12. A methodaccording to claim 1, wherein the myopic defocus area has a focal powerthat is about 2 dioptres less negative than the focal power of thevision correction area.
 13. A method of manufacturing a contact lenssystem or kit for treating or slowing the progression of myopia of aperson, comprising: providing two or more contact lenses which may bethe same or different, at least one of which comprises a visioncorrection area for correcting the myopic vision of the person byproviding a focussed retinal image; and a myopic defocus area forsimultaneously presenting a myopic defocused image to the person whenthe contact lens or contact lenses are worn by the person, wherein thefocussed retinal image and the myopic defocused image lie over the sameretinal areas.
 14. A method according to claim 13, wherein the myopicdefocus area has a focal power that is up to 5 dioptres less negativethan the focal power of the vision correction area.